1. Field of the Invention
The present invention relates to a process for preparing a phenolic polymer using a phenothiazine-based mediator, in particular, to a process for preparing a phenolic polymer by polymerizing phenolic monomers by use of a phenothiazine-based mediator in the presence of a peroxidase biocatalyst and an oxidant, thereby dramatically improving the enzyme reactivity of the peroxidase.
The phenolic polymers prepared according to the polymerization of this invention maintain unsaturated hydrocarbon groups linked to their side chains, so that they are very useful as a curing resin because they can easily form coatings through radical curing. In addition, the coatings formed using the curing resin have antioxidative effect and lower surface energy, so that they can prevent physical attachment of marine living beings. Because the antifouling-causing functional groups are not consumed, the coatings exhibit continuous durability.
2. Description of the Related Art
Phenolic polymers are known to be useful as paints and various coating materials, due to their excellent anti-corrosiveness and capability of forming a firm coating.
For synthesizing phenolic polymers chemically, formalin or hexamethylene tetraamine generated by the condensation of formaldehyde and ammonia is employed in high-temperature polymerization. However, this method some shortcomings in that formalin and formaldehyde are toxic and unreacted reactants toxic to environment and human body remain after the reaction. In addition, when phenolic polymers are synthesized using chemicals such as formalin, the double bonds of a lipid group side chain linked to the phenolic polymers are consumed, so that the resulting phenolic polymers is unlikely to form a coating due to the difficulty in setting by radical reaction.
Therefore, a biochemical preparation using a biocatalyst is recognized as a preferred environment-friendly approach instead of chemical synthesis using toxic materials.
Where phenolic polymers are synthesized using a biocatalyst such as an enzyme, it is essential to establish optimal polymerization conditions in consideration of substrate specificity of the enzyme. For example, a polymer derived from 4-methoxybenzyl alcohol and 2-hydroxy-4-methoxyphenyl acetic acid may not be synthesized using unassisted lignin peroxidase. In contrast, the presence of a mediator such as veratryl alcohol allows the polymerization to be promoted (Harvey et al., FEBS Lett. 195:242-246 (1986)). Furthermore, it has been known that phenolic compounds having significantly long alkyl chains at their meta-position cannot be polymerized by use of horseradish peroxidase. As discussed above, the polymerization of phenol compounds using a biocatalyst demands the establishment of optimal polymerization conditions because of substrate specificity of the enzyme.
The present inventors have conducted extensive research to develop a novel polymerization system which is applicable to all peroxidase biocatalysts generally known to be involved in the polymerization of phenolic monomers, and as a result, it has been found that phenothiazine derivatives could serve as mediators to activate enzymatic reaction of general peroxidases.
Accordingly, it is an object of this invention to provide a process for preparing a phenolic polymer by using a phenothiazine derivative as a mediator in a polymerization system of phenolic monomers using a general peroxidase biocatalyst.
Further, it is another object of this invention to provide use of the obtained phenolic polymers for preparing radical-curing resin.
Still further, it is another object of this invention to provide a coating material comprising the curing resin.